Lo phase correction for aas with multiple rfic

ABSTRACT

Systems and methods are disclosed for correcting Local Oscillator (LO) phase misalignment between different Radio Frequency Integrated Circuits (RFIC) of an Advanced Antenna System (AAS).

This application is a continuation of U.S. patent application Ser. No.16/972,882, filed Dec. 7, 2020, which is a 35 U.S.C. § 371 nationalphase filing of International Application No. PCT/EP2018/064795, filedJun. 5, 2018, the disclosures of which are incorporated herein byreference in their entireties.

TECHNICAL FIELD

Systems and methods are disclosed herein that relate to an AdvancedAntenna System (AAS) for a radio node such as, e.g., a base station in acellular communications system and, more particularly, relate to systemsand methods for Local Oscillator (LO) phase correction for an AAS withmultiple Radio Frequency Integrated Circuits (RFICs) that share a commonexternal LO reference.

BACKGROUND

An Advanced Antenna System (AAS) is an antenna system utilized by radionodes, such as a base station in a cellular communications network, toperform analog beamforming. An AAS has many antenna elements, where eachantenna element is connected to radio front-end that includes atransmitter and a receiver along with a phase tuner and a gain stage toapply desired phase and gain adjustments for, e.g., analog beamforming.Within the AAS, multiple Radio Frequency Integrated Circuits (RFICs) maybe used, each having its own Radio Frequency (RF) and, in some cases,Intermediate Frequency (IF) mixing stages. A common Local Oscillator(LO) source is used to provide a reference LO signal to the RFICs. Forvery high frequencies, each RFIC may include circuitry (e.g., frequencymultiplier(s) and/or divider(s)) used to translate the reference LOsignal to the desired RF and, in some cases, IF frequencies. Generatingthe desired IF/RF frequencies on the RFIC is beneficial, particularlyfor very high frequencies, in order to avoid long routing andcorresponding losses.

As described herein, the inventors have found that phase misalignmentbetween different RFICs in such an AAS may occur. For instance, for highfrequency, it is beneficial to use a scheme where each RFIC hascircuitry to generate the RF LO, and in some cases the IF LO, from alower frequency reference LO source. In such a case, the RF LO can beobtained by a frequency multiplier which is fed by the reference LOsource, while the IF LO can be obtained from a frequency divider(divides by powers of 2) that is fed by RF LO. The inventors have foundthat, for LO generation circuitry designs that include a frequencydivider, the generated LO may have a phase sift (e.g., a phase shift of180 degrees in the case of a divide by 2). This can therefore lead to asituation where different RFICs that share a common external LOreference may not be phase aligned. This phase misalignment canadversely affect the performance of the system. As such, there is a needfor systems and methods for correcting phase misalignment betweenmultiple RFICs in an AAS.

SUMMARY

Systems and methods are disclosed for correcting Local Oscillator (LO)phase misalignment between different Radio Frequency Integrated Circuits(RFIC) of an Advanced Antenna System (AAS). In some embodiments, asystem comprises a radio system comprising two or more RFICs. Each RFICcomprises LO generation circuitry, processing circuitry, and a pluralityof antenna elements. The LO generation circuitry comprises a frequencydivider. Using the frequency divider, the LO generation circuitry isconfigured to generate a LO signal based on a reference LO signal froman external LO source. The processing circuitry is configured toupconvert signals to be transmitted by the plurality of antenna elementsand/or downconvert signals received via the plurality of antennaelements based on the LO signal. The system further comprises aprocessing unit adapted to, for a first RFIC pair comprising two of thetwo or more RFICs, namely a first RFIC and a second RFIC, obtain a firstnear-field power measurement via a receive antenna element locatedeither in the first RFIC or the second RFIC while: (a) a test signal istransmitted via a first transmit antenna element located in the firstRFIC and a second transmit antenna element located in the second RFIC,and (b) the phase state of the second RFIC is a first LO phase state.The first transmit antenna element for the first RFIC pair is one of theplurality of antenna elements located in the first RFIC that isconfigured as a transmit antenna element. The second transmit antennaelement for the first RFIC pair is one of the plurality of antennaelements located in the second RFIC that is configured as a transmitantenna element. The receive antenna element for the first RFIC pair iseither: (a) one of the plurality of antenna elements in the first RFICthat is configured as a receive antenna element or (b) one of theplurality of antenna elements comprised in the second RFIC that isconfigured as a receive antenna element. The processing unit is furtheradapted to, for the first RFIC pair, obtain a second near-field powermeasurement via the receive antenna element while a test signal istransmitted via the first transmit antenna element and the secondtransmit antenna element and the phase state of the second RFIC is asecond LO phase state. In some embodiments, the second LO phase state isa state in which the phase of the LO signal for the second RFIC isshifted by 180 degrees relative to the phase of the LO signal for thesecond RFIC when the phase state of the second RFIC is the first LOphase state. The processing unit is further adapted to, for the firstRFIC pair, determine which of the first LO phase state and the second LOphase state for the second RFIC results in phase alignment between theLO signals for the first RFIC and the second RFIC based on apredetermined relationship between near-field power measurements andphase alignment between the LO signals for the first RFIC and the secondRFIC, and set the phase state of the second RFIC to the determined LOphase state. In this manner, LO phase misalignment between the pair ofRFICs can quickly be detected and corrected.

In some embodiments, the first transmit antenna element, the secondtransmit antenna element, and the receive antenna element are chosensuch that the coupling between the first transmit antenna element andthe receive antenna element is symmetrical to the coupling between thesecond transmit antenna element and the receive antenna element. Inaddition or alternatively, in some embodiments, the first transmitantenna element, the second transmit antenna element, and the receiveantenna element are chosen such that the coupling between the firsttransmit antenna element and the receive antenna element is notorthogonal to the coupling between the second transmit antenna elementand the receive antenna element.

In some embodiments, for each RFIC of the two or more RFICs, theplurality of antenna elements comprised in the RFIC are dual-polarizedantenna elements, the first transmit antenna element and the secondtransmit antenna element are configured in one polarization, while thereceive antenna element is configured in the opposite polarization.

In some embodiments, the predetermined relationship between near-fieldpower measurements and phase alignment between the LO signals for thefirst RFIC and the second RFIC is that: if the first near-field powermeasurement is greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare misaligned when the phase state of the second RFIC is the first LOphase state and aligned when the phase state of the second RFIC is thesecond LO phase state; and, if the first near-field power measurement isnot greater than the second near-field power measurement, then thephases of the LO signals for the first RFIC and the second RFIC arealigned when the phase state of the second RFIC is the first LO phasestate and misaligned when the phase state of the second RFIC is thesecond LO phase state. The determined phase state for the second RFIC isthe second LO phase state if the first near-field power measurement isgreater than the second near-field power measurement and is the first LOphase state if the first near-field power measurement is not greaterthan the second near-field power measurement.

In some other embodiments, the predetermined relationship betweennear-field power measurements and phase alignment between the LO signalsfor the first RFIC and the second RFIC is that: if the first near-fieldpower measurement is greater than the second near-field powermeasurement, then the phases of the LO signals for the first RFIC andthe second RFIC are aligned when the phase state of the second RFIC isthe first LO phase state and misaligned when the phase state of thesecond RFIC is the second LO phase state; and if the first near-fieldpower measurement is not greater than the second near-field powermeasurement, then the phases of the LO signals for the first RFIC andthe second RFIC are misaligned when the phase state of the second RFICis the first LO phase state and aligned when the phase state of thesecond RFIC is the second LO phase state. The determined phase state forthe second RFIC is the first LO phase state if the first near-fieldpower measurement is greater than the second near-field powermeasurement and is the second LO phase state if the first near-fieldpower measurement is not greater than the second near-field powermeasurement.

In some embodiments, the processing unit is further adapted to, for asecond RFIC pair comprising two of the two or more RFICs, namely thefirst RFIC and a third RFIC, obtain a first near-field power measurementfor the second RFIC pair via a receive antenna element for the secondRFIC pair that is located either in the first RFIC or the third RFICwhile: (a) a test signal is transmitted via a first transmit antennaelement for the second RFIC pair that is located in the first RFIC and asecond transmit antenna element for the second RFIC pair that is locatedin the third RFIC and (b) the phase state of the third RFIC is a firstLO phase state. The first transmit antenna element for the second RFICpair is one of the plurality of antenna elements comprised in the firstRFIC that is configured as a transmit antenna element. The secondtransmit antenna element for the second RFIC pair is one of theplurality of antenna elements comprised in the third RFIC that isconfigured as a transmit antenna element. The receive antenna elementfor the second RFIC pair is either: (a) one of the plurality of antennaelements in the first RFIC that is configured as a receive antennaelement or (b) one of the plurality of antenna elements in the thirdRFIC that is configured as a receive antenna element. The processingunit is further adapted to, for the second RFIC pair, obtain a secondnear-field power measurement via the receive antenna element for thesecond RFIC pair while a test signal is transmitted via the firsttransmit antenna element for the second RFIC pair and the secondtransmit antenna element for the second RFIC pair and the phase state ofthe third RFIC is a second LO phase state, wherein the second LO phasestate is a state in which the phase of the LO signal for the third RFICis shifted by 180 degrees relative to the phase of the LO signal for thethird RFIC when the phase state of the third RFIC is the first LO phasestate. The processing unit is further adapted to, for the second RFICpair, determine which of the first LO phase state and the second LOphase state for the third RFIC results in phase alignment between the LOsignals for the first RFIC and the third RFIC based on a predeterminedrelationship between near-field power measurements and phase alignmentbetween the LO signals for the first RFIC and the third RFIC, and setthe phase state of the third RFIC to the determined LO phase state.

In some embodiments, a system comprises a radio system comprising two ormore RFICs. Each RFIC comprises LO generation circuitry, processingcircuitry, and a plurality of antenna elements. The LO generationcircuitry comprises a frequency divider. Using the frequency divider,the LO generation circuitry is configured to generate a LO signal basedon a reference LO signal from an external LO source. The processingcircuitry is configured to upconvert signals to be transmitted by theplurality of antenna elements and/or downconvert signals received viathe plurality of antenna elements based on the LO signal. The systemfurther comprises a processing unit adapted to, for a fist RFIC paircomprising two of the two or more RFICs, namely a first RFIC and asecond RFIC, obtain a first near-field power measurement via a firstreceive antenna element located in the first RFIC and a second receiveantenna element located in the second RFIC while: (a) a test signal istransmitted via a transmit antenna element located either in the firstRFIC or the second RFIC and (b) a phase state of the second RFIC is afirst LO phase state. The first receive antenna element for the firstRFIC pair is one of the plurality of antenna elements in the first RFICthat is configured as a receive antenna element. The second receiveantenna element for the first RFIC pair is one of the plurality ofantenna elements in the second RFIC that is configured as a receiveantenna element. The transmit antenna element for the first RFIC pair iseither: (a) one of the plurality of antenna elements in the first RFICthat is configured as a transmit antenna element or (b) one of theplurality of antenna elements in the second RFIC that is configured as atransmit antenna element. The processing unit is further adapted to, forthe first RFIC pair, obtain a second near-field power measurement viathe first receive antenna element and the second receive antenna elementwhile a test signal is transmitted via the transmit antenna element andthe phase state of the second RFIC is a second LO phase state. In someembodiments, the second LO phase state is a state in which the phase ofthe LO signal for the second RFIC is shifted by 180 degrees relative tothe phase of the LO signal for the second RFIC when the phase state ofthe second RFIC is the first LO phase state. The processing unit isfurther adapted to, for the first RFIC pair, determine which of thefirst LO phase state and the second LO phase state for the second RFICresults in phase alignment between the LO signals for the first RFIC andthe second RFIC based on a predetermined relationship between near-fieldpower measurements and phase alignment between the LO signals for thefirst RFIC and the second RFIC, and set the phase state of the secondRFIC to the determined LO phase state.

In some embodiments, the first receive antenna element, the secondreceive antenna element, and the transmit antenna element are chosensuch that the coupling between the first receive antenna element and thetransmit antenna element is symmetrical to the coupling between thesecond receive antenna element and the transmit antenna element. Inaddition or alternatively, in some embodiments, the first receiveantenna element, the second receive antenna element, and the transmitantenna element are chosen such that the coupling between the firstreceive antenna element and the transmit antenna element is notorthogonal to the coupling between the second receive antenna elementand the transmit antenna element.

In some embodiments, for each RFIC of the two or more RFICs, theplurality of antenna elements comprised in the RFIC are dual-polarizedantenna elements, the first receive antenna element and the secondreceive antenna element are configured in one polarization, and thetransmit antenna element is configured in the opposite polarization.

In some embodiments, the predetermined relationship between near-fieldpower measurements and phase alignment between the LO signals for thefirst RFIC and the second RFIC is that: if the first near-field powermeasurement is greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare misaligned when the phase state of the second RFIC is the first LOphase state and aligned when the phase state of the second RFIC is thesecond LO phase state; and if the first near-field power measurement isnot greater than the second near-field power measurement, then thephases of the LO signals for the first RFIC and the second RFIC arealigned when the phase state of the second RFIC is the first LO phasestate and misaligned when the phase state of the second RFIC is thesecond LO phase state. The determined phase state for the second RFIC isthe second LO phase state if the first near-field power measurement isgreater than the second near-field power measurement and is the first LOphase state if the first near-field power measurement is not greaterthan the second near-field power measurement.

In some embodiments, the predetermined relationship between near-fieldpower measurements and phase alignment between the LO signals for thefirst RFIC and the second RFIC is that: if the first near-field powermeasurement is greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare aligned when the phase state of the second RFIC is the first LOphase state and misaligned when the phase state of the second RFIC isthe second LO phase state; and, if the first near-field powermeasurement is not greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare misaligned when the phase state of the second RFIC is the first LOphase state and aligned when the phase state of the second RFIC is thesecond LO phase state. The determined phase state for the second RFIC isthe first LO phase state if the first near-field power measurement isgreater than the second near-field power measurement and is the secondLO phase state if the first near-field power measurement is not greaterthan the second near-field power measurement.

In some embodiments, the processing unit is further adapted to, for asecond RFIC pair comprising two of the two or more RFICs, namely thefirst RFIC and a third RFIC, obtain a first near-field power measurementfor the second RFIC pair via a first receive antenna element for thesecond RFIC pair that is located in the first RFIC and a second receiveantenna element for the second RFIC pair that is located in the thirdRFIC while: (a) a test signal is transmitted via a transmit antennaelement for the second RFIC pair that is located either in the firstRFIC or the third RFIC and (b) a phase state of the third RFIC is afirst LO phase state. The first receive antenna element for the secondRFIC pair is one of the plurality of antenna elements comprised in thefirst RFIC that is configured as a receive antenna element. The secondreceive antenna element for the second RFIC pair is one of the pluralityof antenna elements comprised in the third RFIC that is configured as areceive antenna element. The transmit antenna element for the secondRFIC pair is either: (a) one of the plurality of antenna elements in thefirst RFIC that is configured as a transmit antenna element or (b) oneof the plurality of antenna elements in the third RFIC that isconfigured as a transmit antenna element. The processing unit is furtheradapted to, for the second RFIC pair, obtain a second near-field powermeasurement via the first receive antenna element for the second RFICpair and the second receive antenna element for the second RFIC pairwhile: (a) a test signal is transmitted via the transmit antenna elementfor the second RFIC pair and the phase state of the third RFIC is asecond LO phase state, wherein the second LO phase state is a state inwhich the phase of the LO signal for the third RFIC is shifted by 180degrees relative to the phase of the LO signal for the third RFIC whenthe phase state of the third RFIC is the first LO phase state. Theprocessing unit is further adapted to, for the second RFIC pair,determine which of the first LO phase state and the second LO phasestate for the third RFIC results in phase alignment between the LOsignals for the first RFIC and the third RFIC based on a predeterminedrelationship between near-field power measurements and phase alignmentbetween the LO signals for the first RFIC and the third RFIC, and setthe phase state of the third RFIC to the determined LO phase state.

Embodiments of a method for self-testing a system to correct for LOphase misalignment between RFICs is also provided. In some embodiments,a method for self-testing of a system is provided, where the systemcomprises a radio system comprising two or more RFICs. Each RFICcomprises LO generation circuitry, processing circuitry, and a pluralityof antenna elements. The LO generation circuitry comprises a frequencydivider. Using the frequency divider, the LO generation circuitry isconfigured to generate a LO signal based on a reference LO signal froman external LO source. The processing circuitry is configured toupconvert signals to be transmitted by the plurality of antenna elementsand/or downconvert signals received via the plurality of antennaelements based on the LO signal. The method comprises, for a first RFICpair comprising two of the two or more RFICs, namely a first RFIC and asecond RFIC, obtaining a first near-field power measurement via areceive antenna element located either in the first RFIC or the secondRFIC while: (a) a test signal is transmitted via a first transmitantenna element located in the first RFIC and a second transmit antennaelement located in the second RFIC and (b) a phase state of the secondRFIC is a first LO phase state. The first transmit antenna element forthe first RFIC pair is one of the plurality of antenna elements locatedin the first RFIC that is configured as a transmit antenna element. Thesecond transmit antenna element for the first RFIC pair is one of theplurality of antenna elements located in the second RFIC that isconfigured as a transmit antenna element. The receive antenna elementfor the first RFIC pair is either: (a) one of the plurality of antennaelements in the first RFIC that is configured as a receive antennaelement or (b) one of the plurality of antenna elements in the secondRFIC that is configured as a receive antenna element. The method furthercomprises, for the first RFIC pair, obtaining a second near-field powermeasurement via the receive antenna element while a test signal istransmitted via the first transmit antenna element and the secondtransmit antenna element and the phase state of the second RFIC is asecond LO phase state. In some embodiments, the second LO phase state isa state in which the phase of the LO signal for the second RFIC isshifted by 180 degrees relative to the phase of the LO signal for thesecond RFIC when the phase state of the second RFIC is the first LOphase state. The method further comprises, for the first RFIC pair,determining which of the first LO phase state and the second LO phasestate for the second RFIC results in phase alignment between the RF LOsignals for the first RFIC and the second RFIC based on a predeterminedrelationship between near-field power measurements and phase alignmentbetween the RF LO signals for the first RFIC and the second RFIC, andsetting the phase state of the second RFIC to the determined LO phasestate.

In some embodiments, the first transmit antenna element, the secondtransmit antenna element, and the receive antenna element are chosensuch that the coupling between the first transmit antenna element andthe receive antenna element is symmetrical to the coupling between thesecond transmit antenna element and the receive antenna element.

In some embodiments, for each RFIC of the two or more RFICs, theplurality of antenna elements comprised in the RFIC are dual-polarizedantenna elements, the first and second transmit antenna elements areconfigured in a first polarization, and the receive antenna element isconfigured in a second polarization. In addition or alternatively, insome embodiments, the first transmit antenna element, the secondtransmit antenna element, and the receive antenna element are chosensuch that the coupling between the first transmit antenna element andthe receive antenna element is not orthogonal to the coupling betweenthe second transmit antenna element and the receive antenna element.

In some embodiments, the predetermined relationship between near-fieldpower measurements and phase alignment between the LO signals for thefirst RFIC and the second RFIC is that: if the first near-field powermeasurement is greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare misaligned when the phase state of the second RFIC is the first LOphase state and aligned when the phase state of the second RFIC is thesecond LO phase state; and, if the first near-field power measurement isnot greater than the second near-field power measurement, then thephases of the LO signals for the first RFIC and the second RFIC arealigned when the phase state of the second RFIC is the first LO phasestate and misaligned when the phase state of the second RFIC is thesecond LO phase state. Determining which of the first LO phase state andthe second LO phase state for the second RFIC results in phase alignmentbetween the LO signals for the first RFIC and the second RFIC comprises:determining that the second LO phase state for the second RFIC resultsin phase alignment between the LO signals for the first RFIC and thesecond RFIC if the first near-field power measurement is greater thanthe second near-field power measurement, and determining that the firstLO phase state for the second RFIC results in phase alignment betweenthe LO signals for the first RFIC and the second RFIC if the firstnear-field power measurement is not greater than the second near-fieldpower measurement.

In some embodiments, the predetermined relationship between near-fieldpower measurements and phase alignment between the LO signals for thefirst RFIC and the second RFIC is that: if the first near-field powermeasurement is greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare aligned when the phase state of the second RFIC is the first LOphase state and misaligned when the phase state of the second RFIC isthe second LO phase state; and, if the first near-field powermeasurement is not greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare misaligned when the phase state of the second RFIC is the first LOphase state and aligned when the phase state of the second RFIC is thesecond LO phase state. Determining which of the first LO phase state andthe second LO phase state for the second RFIC results in phase alignmentbetween the LO signals for the first RFIC and the second RFIC comprises:determining that the first LO phase state for the second RFIC results inphase alignment between the LO signals for the first RFIC and the secondRFIC if the first near-field power measurement is greater than thesecond near-field power measurement, and determining that the second LOphase state for the second RFIC results in phase alignment between theLO signals for the first RFIC and the second RFIC if the firstnear-field power measurement is not greater than the second near-fieldpower measurement.

In some embodiments, the method further comprises, for a second RFICpair comprising two of the two or more RFICs, namely the first RFIC anda third RFIC, obtaining a first near-field power measurement for thesecond RFIC pair via a receive antenna element for the second RFIC pairthat is located either in the first RFIC or the third RFIC while: (a) atest signal is transmitted via a first transmit antenna element for thesecond RFIC pair that is located in the first RFIC and a second transmitantenna element for the second RFIC pair that is located in the thirdRFIC and (b) a phase state of the third RFIC is a first LO phase state.The first transmit antenna element for the second RFIC pair is one ofthe plurality of antenna elements in the first RFIC that is configuredas a transmit antenna element. The second transmit antenna element forthe second RFIC pair is one of the plurality of antenna elements in thethird RFIC that is configured as a transmit antenna element. The receiveantenna element for the second RFIC pair is either: (a) one of theplurality of antenna elements in the first RFIC that is configured as areceive antenna element or (b) one of the plurality of antenna elementsin the third RFIC that is configured as a receive antenna element. Themethod further comprises, for the second RFIC pair, obtaining a secondnear-field power measurement via the receive antenna element for thesecond RFIC pair while a test signal is transmitted via the firsttransmit antenna element for the second RFIC pair and the secondtransmit antenna element for the second RFIC pair and the phase state ofthe third RFIC is a second LO phase state, wherein the second LO phasestate is a state in which the phase of the LO signal for the third RFICis shifted by 180 degrees relative to the phase of the LO signal for thethird RFIC when the phase state of the third RFIC is the first LO phasestate. The method further comprises, for the second RFIC pair,determining which of the first LO phase state and the second LO phasestate for the third RFIC results in phase alignment between the LOsignals for the first RFIC and the third RFIC based on a predeterminedrelationship between near-field power measurements and phase alignmentbetween the LO signals for the first RFIC and the third RFIC, andsetting the phase state of the third RFIC to the determined LO phasestate.

In some embodiments, a method for self-testing of a system is provided,where the system comprises a radio system comprising two or more RFICs.Each RFIC comprises LO generation circuitry, processing circuitry, and aplurality of antenna elements. The LO generation circuitry comprises afrequency divider. Using the frequency divider, the LO generationcircuitry is configured to generate a LO signal based on a reference LOsignal from an external LO source. The processing circuitry isconfigured to upconvert signals to be transmitted by the plurality ofantenna elements and/or downconvert signals received via the pluralityof antenna elements based on the LO signal. The method comprises, for afirst RFIC pair comprising two of the two or more RFICs, namely a firstRFIC and a second RFIC, obtaining a first near-field power measurementvia a first receive antenna element located in the first RFIC and asecond receive antenna element located in the second RFIC while: (a) atest signal is transmitted via a transmit antenna element located eitherin the first RFIC or the second RFIC and (b) a phase state of the secondRFIC is a first LO phase state. The first receive antenna element is oneof the plurality of antenna elements in the first RFIC that isconfigured as a receive antenna element. The second receive antennaelement is one of the plurality of antenna elements in the second RFICthat is configured as a receive antenna element. The transmit antennaelement is either: (a) one of the plurality of antenna elements in thefirst RFIC that is configured as a transmit antenna element or (b) oneof the plurality of antenna elements in the second RFIC that isconfigured as a transmit antenna element. The method further comprises,for the first RFIC pair, obtaining a second near-field power measurementvia the first receive antenna element and the second receive antennaelement while a test signal is transmitted via the transmit antennaelement and the phase state of the second RFIC is a second LO phasestate. In some embodiments, the second LO phase state is a state inwhich the phase of the LO signal for the second RFIC is shifted by 180degrees relative to the phase of the LO signal for the second RFIC whenthe phase state of the second RFIC is the first LO phase state. Themethod further comprises, for the first RFIC pair, determining which ofthe first LO phase state and the second LO phase state for the secondRFIC results in phase alignment between the LO signals for the firstRFIC and the second RFIC based on a predetermined relationship betweennear-field power measurements and phase alignment between the LO signalsfor the first RFIC and the second RFIC, and setting the phase state ofthe second RFIC to the determined LO phase state.

In some embodiments, the first receive antenna element, the secondreceive antenna element, and the transmit antenna element are chosensuch that the coupling between the first receive antenna element and thetransmit antenna element is symmetrical to the coupling between thesecond receive antenna element and the transmit antenna element. Inaddition or alternatively, in some embodiments, the first receiveantenna element, the second receive antenna element, and the transmitantenna element are chosen such that the coupling between the firstreceive antenna element and the transmit antenna element is notorthogonal to the coupling between the second receive antenna elementand the transmit antenna element.

In some embodiments, for each RFIC of the two or more RFICs, theplurality of antenna elements comprised in the RFIC are dual-polarizedantenna elements, the first receive element and the second receiveantenna element are configured in one polarization, and the transmitantenna element is configured in the opposite second polarization.

In some embodiments, the predetermined relationship between near-fieldpower measurements and phase alignment between the LO signals for thefirst RFIC and the second RFIC is that: if the first near-field powermeasurement is greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare misaligned when the phase state of the second RFIC is the first LOphase state and aligned when the phase state of the second RFIC is thesecond LO phase state; and, if the first near-field power measurement isnot greater than the second near-field power measurement, then thephases of the LO signals for the first RFIC and the second RFIC arealigned when the phase state of the second RFIC is the first LO phasestate and misaligned when the phase state of the second RFIC is thesecond LO phase state. Determining which of the first LO phase state andthe second LO phase state for the second RFIC results in phase alignmentbetween the LO signals for the first RFIC and the second RFIC comprises:determining that the second LO phase state for the second RFIC resultsin phase alignment between the LO signals for the first RFIC and thesecond RFIC if the first near-field power measurement is greater thanthe second near-field power measurement, and determining that the firstLO phase state for the second RFIC results in phase alignment betweenthe LO signals for the first RFIC and the second RFIC if the firstnear-field power measurement is not greater than the second near-fieldpower measurement.

In some embodiments, the predetermined relationship between near-fieldpower measurements and phase alignment between the LO signals for thefirst RFIC and the second RFIC is that: if the first near-field powermeasurement is greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare aligned when the phase state of the second RFIC is the first LOphase state and misaligned when the phase state of the second RFIC isthe second LO phase state; and, if the first near-field powermeasurement is not greater than the second near-field power measurement,then the phases of the LO signals for the first RFIC and the second RFICare misaligned when the phase state of the second RFIC is the first LOphase state and aligned when the phase state of the second RFIC is thesecond LO phase state. Determining which of the first LO phase state andthe second LO phase state for the second RFIC results in phase alignmentbetween the LO signals for the first RFIC and the second RFIC comprises:determining that the first LO phase state for the second RFIC results inphase alignment between the LO signals for the first RFIC and the secondRFIC if the first near-field power measurement is greater than thesecond near-field power measurement, and determining that the second LOphase state for the second RFIC results in phase alignment between theLO signals for the first RFIC and the second RFIC if the firstnear-field power measurement is not greater than the second near-fieldpower measurement.

In some embodiments, the method further comprises for a second RFIC paircomprising two of the two or more RFICs, namely the first RFIC and athird RFIC, obtaining a first near-field power measurement for thesecond RFIC pair via a first receive antenna element for the second RFICpair that is located in the first RFIC and a second receive antennaelement for the second RFIC pair that is located in the third RFICwhile: (a) a test signal is transmitted via a transmit antenna elementfor the second RFIC pair that is located either in the first RFIC or thethird RFIC and (b) a phase state of the third RFIC is a first LO phasestate. The first receive antenna element for the second RFIC pair is oneof the plurality of antenna elements in the first RFIC that isconfigured as a receive antenna element. The second receive antennaelement for the second RFIC pair is one of the plurality of antennaelements in the third RFIC that is configured as a receive antennaelement. The transmit antenna element for the second RFIC pair iseither: (a) one of the plurality of antenna elements in the first RFICthat is configured as a transmit antenna element or (b) one of theplurality of antenna elements comprised in the third RFIC that isconfigured as a transmit antenna element. The method further comprises,for the second RFIC pair, obtaining a second near-field powermeasurement via the first receive antenna element for the second RFICpair and the second receive antenna element for the second RFIC pairwhile a test signal is transmitted via the transmit antenna element forthe second RFIC pair and the phase state of the third RFIC is a secondLO phase state, wherein the second LO phase state is a state in whichthe phase of the LO signal for the third RFIC is shifted by 180 degreesrelative to the phase of the LO signal for the third RFIC when the phasestate of the third RFIC is the first LO phase state. The method furthercomprises, for the second RFIC pair, determining which of the first LOphase state and the second LO phase state for the third RFIC results inphase alignment between the LO signals for the first RFIC and the thirdRFIC based on a predetermined relationship between near-field powermeasurements and phase alignment between the LO signals for the firstRFIC and the third RFIC, and setting the phase state of the third RFICto the determined LO phase state.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 illustrates one example of a radio system including an AdvancedAntenna System (AAS) including multiple Radio Frequency IntegratedCircuits (RFICs) in accordance with some embodiments of the presentdisclosure;

FIG. 2 illustrates one example of dual-polarized antenna elements;

FIG. 3 illustrates one example of the Intermediate Frequency (IF) andRadio Frequency (RF) Local Oscillator (LO) generation circuitry includedin an RFIC of an AAS in accordance with some embodiments of the presentdisclosure;

FIG. 4 illustrates one example of two possible LO signals that can occurdue to a frequency divider;

FIG. 5 illustrates one example of a system that performs acharacterization and self-test procedure to correct the phase errorbetween different RFICs of the AAS of FIG. 1;

FIG. 6 is a flow chart that illustrates the operation of the processingunit of FIG. 5 to perform a characterization and self-test procedure inaccordance with embodiments of the present disclosure;

FIG. 7 illustrates one example of how the antenna elements of adjacentRFICs are configured for the characterization and self-test procedure;

FIG. 8 is a flow chart that illustrates a characterization procedure fortransmit LOs in accordance with some embodiments of the presentdisclosure;

FIG. 9 is a flow chart that illustrates a characterization procedure forreceive LOs in accordance with some embodiments of the presentdisclosure;

FIG. 10 is a flow chart that illustrates a self-test procedure fortransmit LOs in accordance with some embodiments of the presentdisclosure;

FIG. 11 is a flow chart that illustrates a self-test procedure forreceive LOs in accordance with some embodiments of the presentdisclosure;

FIG. 12 is a flow chart that illustrates a self-test procedure inaccordance with some other embodiments of the present disclosure;

FIG. 13 graphically illustrates how the characterization and self-testprocedures can be performed across many RFICs using one of the RFICs asa reference in accordance with some embodiments of the presentdisclosure;

FIG. 14 illustrates one example of a cellular communications networkaccording to some embodiments of the present disclosure;

FIG. 15 is a schematic block diagram of a radio access node according tosome embodiments of the present disclosure;

FIG. 16 is a schematic block diagram that illustrates a virtualizedembodiment of the radio access node of FIG. 15 according to someembodiments of the present disclosure; and

FIG. 17 is a schematic block diagram of the radio access node of FIG. 15according to some other embodiments of the present disclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent information to enable thoseskilled in the art to practice the embodiments and illustrate the bestmode of practicing the embodiments. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the disclosure and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure.

Systems and methods for correcting phase misalignment between multipleRadio Frequency Integrated Circuits (RFICs) in an Advanced AntennaSystem (AAS) are disclosed. In this regard, FIG. 1 illustrates oneexample of a radio system, which in this disclosure is referred to as aPhased Antenna Array Module (PAAM) 100, that includes an AAS 102including multiple RFICs 104-1 through 104-4 in accordance with someembodiments of the present disclosure. Note that while there are fourRFICs 104 in this example, the PAAM 100 may include any number of two ormore RFICs 104. In this example, each of the RFICs 104 includes fourAntenna Elements (AEs), which are referenced as AE1-AE4. Note, however,that each RFIC 104 may include any number of two or more AEs. As anotherexample, each RFIC 104 may alternatively include 16 AEs.

The RFICs 104-1 through 104-4 receive a reference Local Oscillator (LO)signal from an external reference LO source 106 through a network ofsplitters 108 through 112. In this example, the reference LO source 106is “external” in that it is external to the RFICs 104-1 through 104-4.In this example, the reference LO source 106 is external to the PAAM100. Note that the connectors that connect the outputs of the splitters110 and 112 to the RFICs 104-1 through 104-4 are matched lengthconnectors (i.e., have the same length). In absence of length matching,calibration data can be used to synchronize the LOs of different RFICs104. The AAS 102, and in particular the RFICs 104-1 through 104-4, areconnected to an interface 114 to a processing unit (e.g., processingunit 500 of FIG. 5). As discussed below, the interface 114 provides aninterface to a processing unit (e.g., processing unit 500 of FIG. 5),where the processing unit, for example, provides baseband transmitsignals to the PAAM 100 for transmission by the AAS 102 and receivesbaseband receive signals from the PAAM 100. In addition, as discussedbelow, the processing unit interacts with the PAAM 100 to perform aself-test procedure.

The RFICs 104-1 through 104-4 include LO generation circuitry 116-1through 116-4, Intermediate Frequency (IF) processing circuitry 118-1through 118-4, Radio Frequency (RF) processing circuitry 120-1 through120-4, and multiple AEs (AE1 through AE4). In the example embodimentsdescribed herein, the AEs are arranged in a matrix, or grid. For eachRFIC 104, the LO generation circuitry 116 generates an IF LO signal andan RF LO signal based on the reference LO signal using, e.g., one ormore frequency multipliers and/or one or more frequency dividers. The IFprocessing circuitry 118 uses the IF LO signal to upconvert basebandtransmit signals received from the processing unit from baseband to IFand to downconvert IF receive signals received from the RF processingcircuitry 120 from IF to baseband. The RF processing circuitry 120 usesthe RF LO signal to upconvert IF transmit signals received from the IFprocessing circuitry 118 from IF to RF and to downconvert RF receivesignals received from the AEs (AE1 through AE4) from RF to IF. Notethat, in the example embodiments described herein, the LO generationcircuitry 116 generates separate IF LO signals for transmit and receiveand generates separate RF LO signals for transmit and receive.

In some embodiments, the AEs (AE1 through AE4) of the RFICs 104-1through 104-4 are dual-polarized. As an example, FIG. 2 illustrates oneexample of the AEs (AE1 through AE4) of an RFIC 104 where the AEs (AE1through AE4) are dual-polarized.

FIG. 3 illustrates one example of the LO generation circuitry 116. Inthis example, the LO generation circuitry 116 includes a frequencymultiplier 300 that translates the reference LO signal from somereference LO frequency to a desired frequency for translating from thedesired transmit/receive RF frequency and a desired IF frequency of thetransmit/receive signal. The resulting LO signal is referred to hereinas the RF LO signal. The LO generation circuitry 116 also includes afrequency divider 302 that translates the RF LO signal to a desiredfrequency for translating between the desired IF frequency of thetransmit/receive signal and either baseband or some other IF frequency(denoted in FIG. 3 as IF2).

FIG. 4 illustrates the LO phase mismatch problem that can occur betweenthe different RFICs 104-1 through 104-4 that results from the circuitryused to implement the frequency divider 302. In this example, thereference LO (REF LO) is first multiplied by 4 to generate the RF LO(4×LO). The RF LO is then divided by 2 to generate the divided signal(i.e., 2×LO). As can be seen in FIG. 4, as a result of the circuitryused to implement the frequency divider 302, the divided signal (2×LOsignal) could have either a rising edge or a falling edge in referenceto the RF LO (i.e., the 4×LO signal).

Thus, when each RFIC 104 has its own LO generation circuitry 116including a frequency multiplier/divider, sometimes the generated LOsignals between RFICs 104 are out of phase with each other. Thisphase-misalignment of the LO signals in different RFICs 104 occurs eventhough the actual reference LO signals used by the RFICs 104 are phasealigned. Thus, inside the RFICs 104, the IF/RF LO signals can berandomly out of phase.

As described herein, the LO phase state of the LO generation circuitry116 is controlled such that respective LO signals of different RFICs 104are phase-aligned. In particular, in the example of FIG. 4, the dividedLO signal output by the frequency divider 302 is provided to one inputof a multiplexer, or switch, 304. In addition, phase-shifting circuitry306 applies a 180 degree phase shift to the divided LO signal. Thephase-shifting circuitry 306 may be implemented to, e.g., phase invertthe divided LO signal by flipping p and n in a differential buffer, thepositive and negative parts of a differential pair. The resultingphase-shifted, divided LO signal is provided to another input of themultiplexer 304. The multiplexer 304 outputs the divided LO signal asthe IF LO signal when configured in a first LO phase state and outputsthe phase-shifted, divided LO signal as the IF LO signal when configuredin a second LO phase state. The LO phase state of the LO generationcircuitry 116 is controlled via a LO phase state select input (e.g.,digital input written to a register), which is provided by, e.g., theprocessing unit via the interface 14.

Note that the example of the LO generation circuitry 116 illustrated inFIG. 3 is only an example. In general, the LO generation circuitry 116is any circuitry that generates, based on reference LO signal providedby an external LO source, a LO signal using a frequency divider.Further, while the two LO phase states are provided by the multiplexer304 and the phase-shifting circuitry 306 at the output of the frequencydivider 302 in the example of FIG. 3, the present disclosure is notlimited thereto. Other types of configurations for providing thedifferent LO phase states can be used, as will be appreciated by one ofordinary skill in the art upon reading this disclosure.

It should also be noted that while a 180 degree phase shift is describedherein, other phase-shift amounts may be used. For example, a 180 degreephase shift is suitable when the frequency divider 302 is a divide by 2.However, if the frequency divider 302 divides by some other number(e.g., 4, 8, 16, etc.), other phase-shift amounts (e.g., 90 degree phaseshift, 45 degree phase shift, etc.) can be used.

FIG. 5 illustrates a system including the PAAM 100 of FIG. 1 and aprocessing unit 500 including a characterization and self-test subsystem502 that operates to correct the LO misalignment between the differentRFICs 104-1 through 104-4 of the AAS 102 of the PAAM 100 in accordancewith embodiments of the present disclosure. The characterization andself-test subsystem 502 may be implemented in hardware or a combinationof hardware and software (e.g., software being executed by one or moreprocessor(s)). Note that, while illustrated separately, in someembodiments, the processing unit 500 and, in particular, thecharacterization and self-test subsystem 502, can be implemented in thePAAM 100.

The characterization and self-test subsystem 502 includes a controller504 that operates to, e.g., control the activation and configuration ofthe antenna elements of the RFICs 104-1 through 104-4 duringcharacterization and self-testing, control a phase state of each of theRFICs 104-1 through 104-4, etc. The characterization and self-testsubsystem 502 also includes a signal generator 506 that operates to,e.g., generate test signals and provide those test signals to the PAAM100 for transmission during calibration and self-testing. The testsignals may be, e.g., pseudo-random signals or single tone signals. Thecharacterization and self-test subsystem 502 also includes a measurementprocessing function 508 that receives near-field measurements from thePAAM 100 during calibration and self-testing and processes thosemeasurements as described herein. Note that, as used herein, a “nearfield” measurement is a measurement obtained by a receive antennaelement(s) in an RFIC(s) 104 of the PAAM 100 during transmission of atest signal via a transmit antenna element(s) in an RFIC(s) 104 of thePAAM 100. Conversely, a “far field” measurement is: (a) a measurementmade at a remote receiver during transmission of a test signal by thePAAM 100; or (b) a measurement made via a receive antenna element(s) ofan RFIC(s) 104 of the PAAM 100 during transmission of a test signal by aremote transmitter.

FIG. 6 illustrates the operation of the processing unit 500, and inparticular the characterization and self-test subsystem 502, inaccordance with some embodiments of the present disclosure. Here, adashed box represents an optional step. As illustrated, thecharacterization and self-test subsystem 502 characterizes arelationship between near-field power measurements and LO phasealignment for multiple RFIC pairs (step 600). Each RFIC pair includes areference RFIC. The reference RFIC is one of the RFICs 104. Thecharacterization and self-test subsystem 502 performs a self-testprocedure to determine whether to invert the phase of the LO(s) on eachRFIC 104 (other than the reference RFIC) (step 602). Note that whileillustrated together, the characterization procedure of step 600 and theself-test procedure of step 602 do not need to be performed by the sameprocessing unit 500 for the same PAAM 100. For example, one processingunit 500 may be used to perform the characterization procedure for onePAAM 100, and the results of the characterization may be used by anotherprocessing unit 500 for another PAAM 100. In other words,characterization may, in some embodiments, be performed once for aparticular PAAM design and the results of the characterization then usedfor self-testing of each PAAM 100 produced for that PAAM design.

FIG. 7 illustrates an example antenna element configuration utilized forcharacterization and self-testing in accordance with some embodiments ofthe present disclosure. As illustrated, when performing transmitcharacterization (e.g., in step 600 of FIG. 6), AE4 on RFIC 104-1 isactivated and configured as a receive antenna element (e.g., in verticalpolarization (V-polarization), AE1 on RFIC 104-1 is activated andconfigured as a (reference) transmit antenna element (e.g., inhorizontal polarization (H-polarization), and the AE1s of RFICs 104-2,104-3, and 104-4 are, for respective iterations of the procedure,activated and configured as transmit antenna elements (e.g., inH-polarization). Note that the selection of AE4 on RFIC 104-1 as thereceive AE is only an example. Any AE having symmetrical ornon-orthogonal coupling with the selected transmit AEs on RFICs 104-1through 104-4 can be used.

More specifically, when performing transmit characterization, thecontroller 504 activates AE4 on RFIC 104-1 and configures it as areceive antenna element (e.g., in vertical polarization(V-polarization). The controller 504 also activates AE1 on RFIC 104-1and configures it as a (reference) transmit antenna element (e.g., inH-polarization). Then, multiple iterations of the characterizationprocedure are performed for each pair of RFICs 104. These pairs of RFICs104 are: (IC1,IC2), (IC1,IC3), and (IC1,IC4). Note that RFIC 104-1 isalso referred to herein as IC1, RFIC 104-2 is also referred to herein asIC2, etc.

More specifically, for a first iteration of transmit characterization,the controller 504 activates AE1 on RFIC 104-2 and configures it as atransmit antenna element (e.g., in H-polarization). The signal generator506 generates a test signal and provides the test signal to the PAAM 100for transmission via AE1 on RFIC 104-1 and AE1 on RFIC 104-2. Due tocoupling between the AEs, during transmission of the test signal, acoupled signal is received via AE4 on RFIC 104-1. The power of thisreceived signal is measured (e.g., on the PAAM 100), and the measurementis provided to the measurement processing function 508 where themeasurement is stored as a first near-field power measurement. Duringcharacterization, a corresponding far-field power measurement is alsoobtained and stored as a first far-field power measurement.

The controller 504 then switches the LO phase state of RFIC 104-2. Morespecifically, when obtaining the first near-field and far-field powermeasurements, the LO phase state of the RFIC 104-2 is set to someinitial LO phase state, which is referred to here as a first LO phasestate. The controller 504 switches the LO phase state of the RFIC 104-2to a second LO phase state in which the phase of the LO signal for theRFIC 104-2 is shifted by 180 degrees with respect to the phase of the LOsignal for the RFIC 104-2 when the RFIC 104-2 is in the first LO phasestate. The switching of the phase state of the RFIC 104-2 may beperformed by providing an appropriate digital input (e.g., the LO phasestate select signal in the example of FIG. 3) to the LO generationcircuitry 116. The signal generator 506 then generates a test signal andprovides the test signal to the PAAM 100 for transmission via AE1 onRFIC 104-1 and AE1 on RFIC 104-2 while the RFIC 104-2 is in the secondLO phase state. Again, due to coupling between the AEs, duringtransmission of the test signal, a coupled signal is received via AE4 onRFIC 104-1. The power of this received signal is measured (e.g., on thePAAM 100), and the measurement is provided to the measurement processingfunction 508 where the measurement is stored as a second near-fieldpower measurement. A corresponding far-field power measurement is alsoobtained and stored as a second far-field power measurement. Thisprocess is then repeated for each of the remaining RFIC pairs.

During characterization, it is known that the signals transmitted fromthe two transmit AEs will constructively combine when the LO phases onthe two RFICs IC1 and ICx (where x=2, 3, or 4) are aligned. As such, foreach RFIC pair (IC1,ICx), if the first far-field power measurement isgreater than the second far-field power measurement, it can bedetermined that the LO phases of the two RFICs IC1 and ICx are alignedwhen the RFIC ICx is in the first LO phase state. Otherwise, it can bedetermined that that the LO phases of the two RFICs IC1 and ICx arealigned when the RFIC ICx is in the second LO phase state. For each RFICpair (IC1,ICx), using this information and the first and secondnear-field power measurements for the RFIC pair (IC1,ICx), themeasurement processing function 508 can determine a relationship betweennear-field power measurements for the two RFICs IC1 and ICx and the LOphase alignment of the two RFICs IC1 and ICx. This can be expressed bythe following truth table:

P_(1,x,far) > P_(1,inv(x),far) P_(1,x,near) > P_(1,inv(x),near) B_(1,x)False False True False True False True False False True True Truewhere P_(1,x,far) is the first far-field power measurement for the RFICpair (IC1,ICx), P_(1,inv(x),far) is the second far-field powermeasurement for the RFIC pair (IC1,ICx), P_(1,x,near) is the firstnear-field power measurement for the RFIC pair (IC1,ICx),P_(1,inv(x),near) is the second near-field power measurement for theRFIC pair (IC1,ICx), and B_(1,x) is a Boolean variable that representsthe relationship between the far-field and near-field measurements forthe RFIC pair (IC1,ICx). As can be seen from the table, the Booleanvariable B_(1,x) is TRUE when the far-field and near-field measurementsare positively correlated, i.e.(P_(1,x,near)>P_(1,inv(x),near))==(P_(1,x,far)>P_(1,inv(x),far)); andB_(1,x) is FALSE when the far-field and near-field measurements arenegatively correlated, i.e. (P_(1,x,near)>P_(1,inv(x),near)) is notequal to T(P_(1,x,far)>P_(1,inv(x),far)). Note that the far-fieldmeasurements are directly related to the LO phase state of the RFIC ICxfor which the LOs for the RFIC pair (IC1,ICx) are aligned, i.e. if(P_(1,x,far)>P_(1,inv(x),far)) is TRUE it means that the LOs of the RFICpair (IC1,ICx) are aligned when the LO phase state of the RFIC ICx isthe first LO phase state, otherwise the LOs of the RFIC pair (IC1,ICx)are aligned when the LO phase state of the RFIC ICx is the second LOphase state. Therefore, for an RFIC pair (IC1,ICx), the Boolean variableB_(1,x) captures the relationship between the near-field measurementsand the LO phase state of the RFIC ICx for which the LO phases for theRFIC pair (IC1,ICx) are aligned (i.e., the LO signals of RFICs IC1 andICx are phase-aligned). Once determined, the Boolean values B_(1,x) arestored and used for subsequent self-testing of the PAAM 100 and/or usedfor subsequent testing of other PAAMs 100 (by storing the Boolean valuesB_(1,x) in the processing units 500 used for other PAAMs 100).

A similar characterization procedure can be performed for receiveoperation.

As illustrated, when performing transmit self-testing (e.g., in step 602of FIG. 6), AE4 on RFIC 104-1 is activated and configured as a receiveantenna element (e.g., in V-polarization), AE1 on RFIC 104-1 isactivated and configured as a (reference) transmit antenna element(e.g., in horizontal polarization (H-polarization), and the AE1s ofRFICs 104-2, 104-3, and 104-4 are, for respective iterations of theprocedure, activated and configured as transmit antenna elements (e.g.,in H-polarization).

More specifically, when performing transmit self-testing, the controller504 activates AE4 on RFIC 104-1 and configures it as a receive antennaelement (e.g., in V-polarization). The controller 504 also activates AE1on RFIC 104-1 and configures it as a (reference) transmit antennaelement (e.g., in H-polarization). Then, multiple iterations of theself-testing procedure are performed for each pair of RFICs 104. Thesepairs of RFICs 104 are: (IC1,IC2), (IC1,IC3), and (IC1,IC4). Note thatRFIC 104-1 is also referred to herein as IC1, RFIC 104-2 is alsoreferred to herein as IC2, etc.

More specifically, for a first iteration of transmit self-testing, thecontroller 504 activates AE1 on RFIC 104-2 and configures it as atransmit antenna element (e.g., in H-polarization). The signal generator506 generates a test signal and provides the test signal to the PAAM 100for transmission via AE1 on RFIC 104-1 and AE1 on RFIC 104-2. Due tocoupling between the AEs, during transmission of the test signal, acoupled signal is received via AE4 on RFIC 104-1. The power of thisreceived signal is measured (e.g., on the PAAM 100), and the measurementis provided to the measurement processing function 508 where themeasurement is stored as a first near-field power measurement.

The controller 504 then switches a LO phase state of the RFIC 104-2.More specifically, when obtaining the first near-field and far-fieldpower measurements, the LO phase state of the RFIC 104-2 is set to someinitial LO phase state, which is referred to here as a first LO phasestate. The controller 504 switches the LO phase state of the RFIC 104-2to a second LO phase state in which the phase of the LO signal for theRFIC 104-2 is shifted by 180 degrees with respect to the phase LO signalfor the RFIC 104-2 when the RFIC 104-2 is in the first LO phase state.The signal generator 506 then generates a test signal and provides thetest signal to the PAAM 100 for transmission via AE1 on RFIC 104-1 andAE1 on RFIC 104-2 while the RFIC 104-2 is in the second LO phase state.Again, due to coupling between the AEs, during transmission of the testsignal, a coupled signal is received via AE4 on RFIC 104-1. The power ofthis received signal is measured (e.g., on the PAAM 100), and themeasurement is provided to the measurement processing function 508 wherethe measurement is stored as a second near-field power measurement. Theprocess is repeated for each of the other RFIC pairs.

During self-testing, for each RFIC pair (IC1,ICx), the expressionP_(1,x,near)>P_(1,inv(x),near) is compared against the Boolean variableB_(1,x) representing the relationship between the near-fieldmeasurements and the LO phase state of the RFIC ICx for which the LOphases of the RFIC pair (IC1,ICx) are aligned. If the comparison is TRUE(i.e., if (P_(1,x,near)>P_(1,inv(x),near))==B_(1,x)), then thecontroller 504 determines that the LO phases of the RFIC pair (IC1,ICx)are aligned when the LO phase state of the RFIC ICx is the first LOphase state. Otherwise, the controller 504 determines that the LO phasesof the RFIC pair (IC1,ICx) are aligned when the LO phase state of theRFIC ICx is the second LO phase state. The controller 504 then sets theLO phase state of RFIC ICx to the phase state that results in LO phasealignment.

FIGS. 8 and 9 are flow charts that illustrate the characterizationprocedure of step 600 of FIG. 6 in more detail in accordance with someembodiments of the present disclosure. FIG. 8 illustrates acharacterization procedure for the transmit LOs of the RFICs 104, andFIG. 9 illustrates a characterization procedure for the receive LOs ofthe RFICs 104.

As illustrated in FIG. 8, for transmit, the controller 504 of thecharacterization and self-testing subsystem 502 initializes an index xto a value of 1 (step 800). If the value of x is not greater than thenumber of RFIC pairs to be processed for the characterization procedure(step 802, NO), the controller 504 increments x (step 803) and sets aninitial phase state for RFIC ICx to the first LO phase state (step 804).The controller 504 activates the reference antenna element (e.g., AE1)on the reference RFIC IC1 and activates a test antenna element (e.g.,AE1) on RFIC ICx and configures these two antenna elements as transmitantenna elements, e.g., in the H-polarization (step 806). In addition,the controller 504 activates an antenna element either on RFIC IC1 orICx (e.g., AE4 on RFIC IC1) and configures that antenna element as areceive antenna element, e.g., in the V-polarization (step 808).

While a test signal is transmitted by the PAAM 100 using the twotransmit antenna elements and the LO phase state of RFIC ICx is set tothe first LO phase state, the characterization and self-test subsystem502 obtains a first near-field power measurement (P_(1,x,near)) via thereceive antenna element and also obtains a corresponding first far-fieldpower measurement (P_(1,x,far)) (step 810). More specifically, thecontroller 504 causes the signal generator 506 to generate a test signaland provide the test signal to the PAAM 100 for transmission via the twotransmit antenna elements. Due to coupling, a resulting signal isreceived at the receive antenna element. A power of this signal ismeasured in the PAAM 100 (e.g., in the respective RFIC) to therebyprovide the first near-field power measurement (P_(1,x,near)), which issent to the processing unit 500 and stored. The first far-field powermeasurement (P_(1,x,far)) is made by a remote receiver and returned tothe processing unit 500 and stored.

The controller 504 switches the LO phase state of the RFIC ICx from thefirst LO phase state to the second LO phase state such that the phase ofthe LO signal for the RFIC ICx is shifted by 180 degrees (step 812).While a test signal is transmitted by the PAAM 100 using the twotransmit antenna elements and the LO phase state of RFIC ICx is set tothe second LO phase state, the characterization and self-test subsystem502 obtains a second near-field power measurement (P_(1,inv(x),near))via the receive antenna element and also obtains corresponding secondfar-field power measurement (P_(1,inv(x),far)) (step 814). Morespecifically, the controller 504 causes the signal generator 506 togenerate a test signal and provide the test signal to the PAAM 100 fortransmission via the two transmit antenna elements. Due to coupling, aresulting signal is received at the receive antenna element. A power ofthis signal is measured in the PAAM 100 (e.g., in the respective RFIC)to thereby provide the second near-field power measurement(P_(1,inv(x),near)), which is sent to the processing unit 500 andstored. The second far-field power measurement (P_(1,inv(x),far)) ismade by a remote receiver and returned to the processing unit 500 andstored.

The controller 504 then determines a relationship (e.g., B_(1,x))between the power level of the near-field power measurements for theRFIC pair (IC1,ICx) and the LO phase alignment for the RFIC pair(IC1,ICx) based on the near-field and far-field measurements, asdiscussed above (step 816). This relationship is stored. The processreturns to step 802 and is repeated until the last RFIC pair has beenprocessed.

As illustrated in FIG. 9, for receive characterization, the controller504 of the characterization and self-test subsystem 502 initializes anindex x to a value of 1 (step 900). If the value of x is not greaterthan the number of RFIC pairs to be processed for the characterizationprocedure (step 902, NO), the controller 504 increments x (step 903) andsets an initial phase state for RFIC ICx to the first LO phase state(step 904). The controller 504 activates the reference antenna element(e.g., AE1) on the reference RFIC IC1 and activates a test antennaelement (e.g., AE1) on RFIC ICx and configures these two antennaelements as receive antenna elements, e.g., in the V-polarization (step906). In addition, the controller 504 activates an antenna elementeither on RFIC IC1 or ICx (e.g., AE4 on RFIC IC1) and configures thatantenna element as a transmit antenna element, e.g., in theH-polarization (step 908).

While a test signal is transmitted by the PAAM 100 using the transmitantenna element and the LO phase state of RFIC ICx is set to the firstLO phase state, the characterization and self-test subsystem 502 obtainsa first near-field power measurement (P_(1,x,near)) via the receiveantenna elements and also obtains a corresponding first far-field powermeasurement (P_(1,x,far)) (step 910). Note that the corresponding firstfar-field power measurement (P_(1,x,far)) is obtained based on aseparate signal transmitted to the PAAM 100 from a far-fieldtransmitter. More specifically, the controller 504 causes the signalgenerator 506 to generate a test signal and provide the test signal tothe PAAM 100 for transmission via the transmit antenna element. Due tocoupling, resulting signals are received at the two receive antennaelements. These two receive signals are combined and a power measurementof this combined signal is made in the PAAM 100 (e.g., in the respectiveRFIC) to thereby provide the first near-field power measurement(P_(1,x,near)), which is sent to the processing unit 500 and stored. Thefirst far-field power measurement (P_(1,x,far)) ismade based on a signaltransmitted by a far-field transmitter that is received via the tworeceive antenna elements.

The controller 504 switches the LO phase state of the RFIC ICx from thefirst LO phase state to the second LO phase state such that the phase ofthe LO signal for the RFIC ICx is shifted by 180 degrees (step 912).While a test signal is transmitted by the PAAM 100 using the transmitantenna element and the LO phase state of RFIC ICx is set to the secondLO phase state, the characterization and self-test subsystem 502 obtainsa second near-field power measurement (P_(1,inv(x),near)) via the tworeceive antenna elements and also obtains a corresponding secondfar-field power measurement (P_(1,inv(x),far)) (step 914).

The controller 504 then determines a relationship (e.g., B_(1,x))between the power level of the near-field power measurements for theRFIC pair (IC1,ICx) and the LO phase alignment for the RFIC pair(IC1,ICx) based on the near-field and far-field measurements, asdiscussed above (step 916). This relationship is stored. The processreturns to step 902 and is repeated until the last RFIC pair has beenprocessed.

FIGS. 10 and 11 are flow charts that illustrate the self-test procedureof step 602 of FIG. 6 in more detail in accordance with some embodimentsof the present disclosure. FIG. 10 illustrates a self-test procedure forthe transmit LOs of the RFICs 104, and FIG. 11 illustrates a self-testprocedure for the receive LOs of the RFICs 104.

As illustrated in FIG. 10, for transmit, the controller 504 of thecharacterization and self-test subsystem 502 initializes an index x to avalue of 1 (step 1000). If the value of x is not greater than the numberof RFIC pairs to be processed for the characterization procedure (step1002, NO), the controller 504 increments x (step 1003) and sets aninitial phase state for RFIC ICx to the first LO phase state (step1004). The controller 504 activates the reference antenna element (e.g.,AE1) on the reference RFIC IC1 and activates a test antenna element(e.g., AE1) on RFIC ICx and configures these two antenna elements astransmit antenna elements, e.g., in the H-polarization (step 1006). Inaddition, the controller 504 activates an antenna element either on RFICIC1 or ICx (e.g., AE4 on RFIC IC1) and configures that antenna elementas a receive antenna element, e.g., in the V-polarization (step 1008).

While a test signal is transmitted by the PAAM 100 using the twotransmit antenna elements and the LO phase state of RFIC ICx is set tothe first LO phase state, the characterization and self-test subsystem502 obtains a first near-field power measurement (P_(1,x,near)) via thereceive antenna element (step 1010). More specifically, the controller504 causes the signal generator 506 to generate a test signal andprovide the test signal to the PAAM 100 for transmission via the twotransmit antenna elements. Due to coupling, a resulting signal isreceived at the receive antenna element. A power of this signal ismeasured in the PAAM 100 (e.g., in the respective RFIC) to therebyprovide the first near-field power measurement (P_(1,x,near)), which issent to the processing unit 500 and stored.

The controller 504 switches the LO phase state of the RFIC ICx from thefirst LO phase state to the second LO phase state such that the phase ofthe LO signal for the RFIC ICx is shifted by 180 degrees (step 1012).While a test signal is transmitted by the PAAM 100 using the twotransmit antenna elements and the LO phase state of RFIC ICx is set tothe second LO phase state, the characterization and self-test subsystem502 obtains a second near-field power measurement (P_(1,inv(x),near))via the receive antenna element (step 1014). More specifically, thecontroller 504 causes the signal generator 506 to generate a test signaland provide the test signal to the PAAM 100 for transmission via the twotransmit antenna elements. Due to coupling, a resulting signal isreceived at the receive antenna element. A power of this signal ismeasured in the PAAM 100 (e.g., in the respective RFIC) to therebyprovide the second near-field power measurement (P_(1,inv(x),near)),which is sent to the processing unit 500 and stored.

The controller 504 then determines which of the two near-field powermeasurements (P_(1,x,near) and P_(1,inv(x),near)) result in LO phasealignment between the two RFICs IC1 and ICx based on the knownrelationship (e.g., B_(1,x)) between power level of the near-field powermeasurements for the RFIC pair (IC1,ICx) and LO phase alignment for theRFIC pair (IC1,ICx) (step 1016). For example, as discussed above, insome embodiments, the relationship is expressed as a Boolean valueB_(1,x,) and the first LO phase state is determined to be the LO phasestate that provides LO phase alignment if the expression(P_(1,x,near)>P_(1,inv(x),near))==B_(1,x) is TRUE. Otherwise, the secondLO phase state is determined to be the LO phase state that provides LOphase alignment. The controller 504 then sets the LO phase state of RFICICx to the LO phase stated determined to be the LO phase state thatprovides LO phase alignment between RFIC IC1 and RFIC ICx (step 1018).The process returns to step 1002 and is repeated until the last RFICpair has been processed.

As illustrated in FIG. 11, for receive self-test, the controller 504 ofthe characterization and self-test subsystem 502 initializes an index xto a value of 1 (step 1100). If the value of x is not greater than thenumber of RFIC pairs to be processed for the characterization procedure(step 1102, NO), the controller 504 increments x (step 1103) and sets aninitial phase state for RFIC ICx to the first LO phase state (step1104). The controller 504 activates the reference antenna element (e.g.,AE1) on the reference RFIC IC1 and activates a test antenna element(e.g., AE1) on RFIC ICx and configures these two antenna elements asreceive antenna elements, e.g., in the V-polarization (step 1106). Inaddition, the controller 504 activates an antenna element either on RFICIC1 or ICx (e.g., AE4 on RFIC IC1) and configures that antenna elementas a transmit antenna element, e.g., in the H-polarization (step 1108).

While a test signal is transmitted by the PAAM 100 using the transmitantenna element and the LO phase state of RFIC ICx is set to the firstLO phase state, the characterization and self-test subsystem 502 obtainsa first near-field power measurement (P_(1,x,near)) via the receiveantenna elements (step 1110). More specifically, the controller 504causes the signal generator 506 to generate a test signal and providethe test signal to the PAAM 100 for transmission via the transmitantenna element. Due to coupling, resulting signals are received at thereceive antenna elements. These signals are combined, and the power ofthis combined signal is measured in the PAAM 100 to thereby provide thefirst near-field power measurement (P_(1,x,near)), which is sent to theprocessing unit 500 and stored.

The controller 504 switches the LO phase state of the RFIC ICx from thefirst LO phase state to the second LO phase state such that the phase ofthe LO signal for the RFIC ICx is shifted by 180 degrees (step 1112).While a test signal is transmitted by the PAAM 100 using the transmitantenna element and the LO phase state of RFIC ICx is set to the secondLO phase state, the characterization and self-test subsystem 502 obtainsa second near-field power measurement (P_(1,inv(x),near)) via thereceive antenna elements (step 1114). More specifically, the controller504 causes the signal generator 506 to generate a test signal andprovide the test signal to the PAAM 100 for transmission via thetransmit antenna element. Due to coupling, resulting signals arereceived at the receive antenna elements. These signals are combined,and a power of the combined signal is measured in the PAAM 100 (e.g., inthe respective RFIC) to thereby provide the second near-field powermeasurement (P_(1,inv(x),near)), which is sent to the processing unit500 and stored.

The controller 504 then determines which of the two near-field powermeasurements (P_(1,x,near) and P_(1,inv(x),near)) result in LO phasealignment between the two RFICs IC1 and ICx based on the knownrelationship (e.g., B_(1,x)) between power level of the near-field powermeasurements for the RFIC pair (IC1,ICx) and LO phase alignment for theRFIC pair (IC1,ICx) (step 1116). For example, as discussed above, insome embodiments, the relationship is expressed as a Boolean valueB_(1,x), and the first LO phase state is determined to be the LO phasestate that provides LO phase alignment if the expression(P_(1,x,near)>P_(1,inv(x),near))==B_(1,x) is TRUE. Otherwise, the secondLO phase state is determined to be the LO phase state that provides LOphase alignment. The controller 504 then sets the LO phase state of RFICICx to the LO phase stated determined to be the LO phase state thatprovides LO phase alignment between RFIC IC1 and RFIC ICx (step 1118).The process returns to step 1102 and is repeated until the last RFICpair has been processed.

Note that the basis for the characterization and self-test proceduresdescribed above with respect to FIGS. 7 through 11 is as follows. Forcharacterization and self-testing in the transmit direction, thetransfer function of a system with two transmit antenna elements (AE1located in RFIC IC1, and AE2 located in RFIC IC2) and a single receiveantenna element (AE4 located in RFIC IC1) can be expressed as:

M x_(A1 _ IC 1, A1 _ IC 2) = Tx_(AE 1_ IC 1)C_(AE 1_ IC 1, AE 4_ IC 1)Rx_(AE 4_ IC 1) + Tx_(AE 1_ IC 2)C_(AE 1_ IC 2, AE 4_ IC 1)Rx_(AE 4_ IC 1)e^(i Δ φ_(1, 2))

where:

Tx_(AE1_IC1) is the transfer function of the transmit antenna elementAE1 located in RFIC IC1 (see FIG. 7),

Tx_(AE1_IC2) is the transfer function of the transmit antenna elementAE1 located in RFIC IC2 (see FIG. 7),

C_(AE1_IC1,AE4_IC1) is the coupling between the transmit antenna elementAE1 located in RFIC IC1 and the receive antenna element AE4 located inRFIC IC1,

C_(AE1_IC2,AE4_IC1) is the coupling between the transmit antenna elementAE1 located in RFIC IC2 and the receive antenna element AE4 located inRFIC IC1,

Rx_(AE4_IC1) is the transfer function of the receive antenna element AE4located in RFIC IC1,

Δφ_(1,2) is the LO phase difference between RFIC IC1 and RFIC IC2

Provided that Δφ_(1,2) is either 0 or π radians, and assuming that theAAS 102 has already been calibrated, i.e. Tx_(AE1_IC1)≅Tx_(AE1_IC2), thetransfer function Mx_(A1_IC1,A1_IC2) can be expressed as:

Mx _(A1_IC1,A1_IC2) =Tx _(AE1_IC1)(C _(AE1_IC1,AE4_IC1) ±C_(AE1,IC2,AE4_IC1))Rx _(AE4_IC1)

Likewise, for the other RFIC pairs (IC1,IC3) and (IC1,IC4), the receivedsignal at the receive antenna element can be expressed as:

Mx _(A1_IC1,A1_IC3) =Tx _(AE1_IC1)(C _(AE1_IC1,AE4_IC1) ±C_(AE1_IC3,AE4_IC1))Rx _(AE4_IC1)

and

Mx _(A1_IC1,A1_IC4) =Tx _(AE1_IC1)(C _(AE1_IC1,AE4_IC1) ±C_(AE1_IC4,AE4_IC1))Rx _(AE4_IC1)

From the equations above, it can be seen that, if the transmit antennaelements and the receive antenna element are selected such that there issymmetrical coupling (i.e., such that C_(IC1)≅C_(IC2)≅C_(IC3)≅C_(IC4)),then the power of the received signal will be small when ICx is in oneLO phase state and relatively large when ICx is in the other phasestate.

From the equations above, it can be seen that, as long as the couplingsbetween the transmit antenna elements and the receive antenna element,i.e. C_(AE1_IC1,AE4_IC1) and C_(AE1_IC2,AE4_ICx), are not orthogonal toeach other, the measured power of the received signal, which isproportional to the squared absolute value of the transfer functionMx_(AE1_IC1,AE1_ICx), can have two distinct values based on whether theLO phase state in the RFIC ICx is the first LO phase state or it is thesecond LO phase state. In other words, one power value will correspondto one LO phase state of the RFIC ICx, and a different power value willcorrespond to the opposite LO phase state of the RFIC ICx.

For the specific case, when the couplings between the transmit antennaelements and the receive antenna element, i.e. C_(AE1_IC1,AE4_IC1) andC_(AE1_IC2,AE4_ICx), are “symmetrical,” i.e.C_(AE1_IC1,AE4_IC1)≈C_(AE1_IC1,AE4_ICx) ^(e) ^(tkπ) k=0,1, the twopossible power values will be further apart from each other, allowingfor a larger margin and thus making the method less sensitive to, forexample, noise or external interference. Therefore, this is thepreferred scenario when choosing the transmit and receive antennaelements.

Using this notation, FIG. 12 is a flow chart that illustrates theself-testing procedure of step 602 of FIG. 6 in accordance with someother embodiments of the present disclosure. As illustrated, thecontroller 504 of the characterization and self-test subsystem 502 setsa direction to perform LO phase alignment (step 1200) and set thepolarization (e.g., H-polarization) (step 1202). The controller 504activates a reference measurement antenna element in a differentpolarization than that set in step 1202 (e.g., V-polarization) (step1204). The controller 504 activates a defined element in the referenceRFIC IC1 (step 1206) and sets an RFIC index x=1 (step 1208).

If x<max (where max is the maximum number of RFICs to be tested) (step1210, YES), the controller 504 increments x (step 1211), and activates adefined antenna element in ICx (step 1212). The characterization andself-test subsystem 502 then obtains a first near-field powermeasurement for the RFIC pair (IC1,ICx) as described above (step 1214).The controller 504 toggles, or switches, the LO phase state of the RFICICx (step 1216) and obtains a second near-field power measurement forthe RFIC pair (IC1,ICx) as described above (step 1218). The first andsecond near-field power measurements are checked against target logic(e.g., B_(1,x)) stored in memory (step 1220). In this case, ifXOR((M_(WT)>M_(T)),M)=1 (step 1222, YES), then the polarity (i.e., theLO phase state) of RFIC ICx is kept at the toggled, or switched, LOphase state (step 1224). Otherwise (step 1222, NO), the polarity of RFICICx is set to the default state (i.e., the first LO phase state) (step1226). RFIC ICx is then deactivated (step 1228), and the process returnsto step 1210. Steps 1211 through 1228 are repeated for all of the RFICsto be tested. Once the last RFIC has been tested (i.e., step 1210, NO),the polarization is changed (step 1232) and the process returns (step1234, YES) to step 1202 and the process is repeated for the newpolarization. Once the last polarization is processed (step 1234, NO),the direction is changed (e.g., from transmit self-test to receiveself-test) (step 1236) and, if both transmit and receive directions havenot yet been processed (step 1238, YES), the process returns to step1200 and is repeated for the new direction.

FIG. 13 graphically illustrates one example of how the characterizationand self-test procedures of FIGS. 7 through 12 can be performed acrossmany RFICs 104 using one of the RFICs (e.g., 104-1) as a reference inaccordance with some embodiments of the present disclosure. Asillustrated,

a first characterization/self-test is performed for RFICs IC2, IC7, andIC8 using RFIC IC1 as a reference;

a second characterization/self-test is performed for RFICs IC3 and IC9using RFIC IC2 (or RFIC IC8) as the reference;

a third characterization/self-test is performed for RFICsIC4 and IC10using RFIC IC3 (or RFIC IC9) as the reference;

a fourth characterization/self-test is performed for RFICsIC5 and IC11using RFIC IC4 (or RFIC IC10) as the reference;

a fifth characterization/self-test is performed for RFICsIC6 and IC12using RFIC IC5 (or RFIC IC11) as the reference;

a sixth characterization/self-test is performed for RFICs IC13 and IC14using RFIC IC7 (or RFIC IC 8) as the reference;

a seventh characterization/self-test is performed for RFIC IC15 usingRFIC IC8 (or RFIC IC9 or RFIC IC14) as the reference;

an eighth characterization/self-test is performed for RFIC IC16 usingRFIC IC9 (or RFIC IC10 or RFIC IC15) as the reference;

a ninth characterization/self-test is performed for RFIC IC17 using RFICIC10 (or RFIC IC11 or RFIC IC16) as the reference; and

a tenth characterization/self-test is performed for RFIC IC18 using RFICIC11 (or RFIC IC12 or RFIC IC17) as the reference.

In this manner, RFIC IC1 becomes the main reference RFIC such that theLO phases of all of the RFICs are, after self-testing, aligned with theLO phase of the RFIC IC1. Note that the example described above withrespect to FIG. 13 is only an example. Any suitable pair-wiseself-testing of the RFICs may be used.

Systems and methods are disclosed herein that provide a method fordetecting and correcting LO phase misalignment between the RFICs 104 inthe AAS 102. As described herein, a test signal is transmitted usingdifferent combinations of a limited number of transmit antenna elementsand measured with different combinations of a limited number of receiveantenna elements. Then, power of the resulting received signal ismeasured. This process may be repeated after inverting the LO phasestate of one or more of the RFICs. Then, the measured power value(s) arecompared with information that defines a known relationship between themeasurement value(s) and the LO phase-alignment of the RFICs. From thiscomparison, the RFIC(s) for which the LO phase is misaligned can bedetermined, and the LO phases of those RFIC(s) can be corrected. Thisprocess can be performed with a small number of steps and measurementsand, as such, is very fast.

While not being limited to or by any particular advantage, embodimentsof the present disclosure provide a number of advantages. For example,embodiments disclosed herein enable self-testing and correction of LOphase misalignment between RFICs in the AAS. The embodiments disclosedherein can be used for either analog or digital beamforming. Theembodiments disclosed herein require a small number of steps andmeasurements and, therefore, the correction can be made very quickly.Embodiments of the present disclosure enable detection and correction ofLO phase misalignment between the RFICs of an AAS for both uplink anddownlink when different frequency multipliers and/or dividers are usedfor uplink and downlink.

FIG. 14 illustrates one example of a cellular communications network1400 according to some embodiments of the present disclosure. In theembodiments described herein, the cellular communications network 1400is a Fifth Generation (5G) New Radio (NR) network. In this example, thecellular communications network 1400 includes base stations 1402-1 and1402-2, which in Long Term Evolution (LTE) are referred to as enhancedor evolved Node Bs (eNBs) and in 5G NR are referred to as NR basestations (gNBs), controlling corresponding macro cells 1404-1 and1404-2. The base stations 1402-1 and 1402-2 are generally referred toherein collectively as base stations 1402 and individually as basestation 1402. Likewise, the macro cells 1404-1 and 1404-2 are generallyreferred to herein collectively as macro cells 1404 and individually asmacro cell 1404. The cellular communications network 1400 may alsoinclude a number of low power nodes 1406-1 through 1406-4 controllingcorresponding small cells 1408-1 through 1408-4. The low power nodes1406-1 through 1406-4 can be small base stations (such as pico or femtobase stations) or Remote Radio Heads (RRHs), or the like. Notably, whilenot illustrated, one or more of the small cells 1408-1 through 1408-4may alternatively be provided by the base stations 1402. The low powernodes 1406-1 through 1406-4 are generally referred to hereincollectively as low power nodes 1406 and individually as low power node1406. Likewise, the small cells 1408-1 through 1408-4 are generallyreferred to herein collectively as small cells 1408 and individually assmall cell 1408. The base stations 1402 (and optionally the low powernodes 1406) are connected to a core network 1410.

The base stations 1402 and the low power nodes 1406 provide service towireless devices 1412-1 through 1412-5 in the corresponding cells 1404and 1408. The wireless devices 1412-1 through 1412-5 are generallyreferred to herein collectively as wireless devices 1412 andindividually as wireless device 1412. The wireless devices 1412 are alsosometimes referred to herein as User Equipment devices (UEs).

FIG. 15 is a schematic block diagram of a radio access node 1500according to some embodiments of the present disclosure. The radioaccess node 1500 may be, for example, a base station 1402 or 1406. Asillustrated, the radio access node 1500 includes a control system 1502that includes one or more processors 1504 (e.g., Central ProcessingUnits (CPUs), Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs), and/or the like), memory 1506, and anetwork interface 1508. The one or more processors 1504 are alsoreferred to herein as processing circuitry. In addition, the radioaccess node 1500 includes one or more radio units 1510 that eachincludes one or more transmitters 1512 and one or more receivers 1514coupled to one or more antennas 1516. The radio units 1510 may bereferred to or be part of radio interface circuitry. In someembodiments, the radio unit(s) 1510 is external to the control system1502 and connected to the control system 1502 via, e.g., a wiredconnection (e.g., an optical cable). However, in some other embodiments,the radio unit(s) 1510 and potentially the antenna(s) 1516 areintegrated together with the control system 1502. The one or moreprocessors 1504 operate to provide one or more functions of a radioaccess node 1500 as described herein. In some embodiments, thefunction(s) are implemented in software that is stored, e.g., in thememory 1506 and executed by the one or more processors 1504.

FIG. 16 is a schematic block diagram that illustrates a virtualizedembodiment of the radio access node 1500 according to some embodimentsof the present disclosure. This discussion is equally applicable toother types of network nodes. Further, other types of network nodes mayhave similar virtualized architectures.

As used herein, a “virtualized” radio access node is an implementationof the radio access node 1500 in which at least a portion of thefunctionality of the radio access node 1500 is implemented as a virtualcomponent(s) (e.g., via a virtual machine(s) executing on a physicalprocessing node(s) in a network(s)). As illustrated, in this example,the radio access node 1500 includes the control system 1502 thatincludes the one or more processors 1504 (e.g., CPUs, ASICs, FPGAs,and/or the like), the memory 1506, and the network interface 1508 andthe one or more radio units 1510 that each includes the one or moretransmitters 1512 and the one or more receivers 1514 coupled to the oneor more antennas 1516, as described above. The control system 1502 isconnected to the radio unit(s) 1510 via, for example, an optical cableor the like. The control system 1502 is connected to one or moreprocessing nodes 1600 coupled to or included as part of a network(s)1602 via the network interface 1508. Each processing node 1600 includesone or more processors 1604 (e.g., CPUs, ASICs, FPGAs, and/or the like),memory 1606, and a network interface 1608.

In this example, functions 1610 of the radio access node 1500 describedherein are implemented at the one or more processing nodes 1600 ordistributed across the control system 1502 and the one or moreprocessing nodes 1600 in any desired manner. In some particularembodiments, some or all of the functions 1610 of the radio access node1500 described herein are implemented as virtual components executed byone or more virtual machines implemented in a virtual environment(s)hosted by the processing node(s) 1600. As will be appreciated by one ofordinary skill in the art, additional signaling or communication betweenthe processing node(s) 1600 and the control system 1502 is used in orderto carry out at least some of the desired functions 1610. Notably, insome embodiments, the control system 1502 may not be included, in whichcase the radio unit(s) 1510 communicate directly with the processingnode(s) 1600 via an appropriate network interface(s).

In some embodiments, a computer program including instructions which,when executed by at least one processor, causes the at least oneprocessor to carry out the functionality of radio access node 1500 or anode (e.g., a processing node 1600) implementing one or more of thefunctions 1610 of the radio access node 1500 in a virtual environmentaccording to any of the embodiments described herein is provided. Insome embodiments, a carrier comprising the aforementioned computerprogram product is provided. The carrier is one of an electronic signal,an optical signal, a radio signal, or a computer readable storage medium(e.g., a non-transitory computer readable medium such as memory).

FIG. 17 is a schematic block diagram of the radio access node 1500according to some other embodiments of the present disclosure. The radioaccess node 1500 includes one or more modules 1700, each of which isimplemented in software. The module(s) 1700 provide the functionality ofthe radio access node 1500 described herein. This discussion is equallyapplicable to the processing node 1600 of FIG. 16 where the modules 1700may be implemented at one of the processing nodes 1600 or distributedacross multiple processing nodes 1600 and/or distributed across theprocessing node(s) 1600 and the control system 1502.

Any appropriate steps, methods, features, functions, or benefitsdisclosed herein may be performed through one or more functional unitsor modules of one or more virtual apparatuses. Each virtual apparatusmay comprise a number of these functional units. These functional unitsmay be implemented via processing circuitry, which may include one ormore microprocessor or microcontrollers, as well as other digitalhardware, which may include Digital Signal Processors (DSPs),special-purpose digital logic, and the like. The processing circuitrymay be configured to execute program code stored in memory, which mayinclude one or several types of memory such as Read Only Memory (ROM),Random Access Memory (RAM), cache memory, flash memory devices, opticalstorage devices, etc. Program code stored in memory includes programinstructions for executing one or more telecommunications and/or datacommunications protocols as well as instructions for carrying out one ormore of the techniques described herein. In some implementations, theprocessing circuitry may be used to cause the respective functional unitto perform corresponding functions according one or more embodiments ofthe present disclosure.

While processes in the figures may show a particular order of operationsperformed by certain embodiments of the present disclosure, it should beunderstood that such order is exemplary (e.g., alternative embodimentsmay perform the operations in a different order, combine certainoperations, overlap certain operations, etc.).

At least some of the following abbreviations may be used in thisdisclosure. If there is an inconsistency between abbreviations,preference should be given to how it is used above. If listed multipletimes below, the first listing should be preferred over any subsequentlisting(s).

-   -   5G Fifth Generation    -   AAS Advanced Antenna System    -   AE Antenna Element    -   AF Application Function    -   AMF Access and Mobility Management Function    -   AN Access Network    -   ASIC Application Specific Integrated Circuit    -   AUSF Authentication Server Function    -   CPU Central Processing Unit    -   DN Data Network    -   DSP Digital Signal Processor    -   eNB Enhanced or Evolved Node B    -   FPGA Field Programmable Gate Array    -   GHz Gigahertz    -   gNB New Radio Base Station    -   IF Intermediate Frequency    -   IP Internet Protocol    -   LO Local Oscillator    -   LTE Long Term Evolution    -   NEF Network Exposure Function    -   NF Network Function    -   NR New Radio    -   NRF Network Repository Function    -   NSSF Network Slice Selection Function    -   PAAM Phased Antenna Array Module    -   PCF Policy Control Function    -   QoS Quality of Service    -   RAM Random Access Memory    -   RAN Radio Access Network    -   RF Radio Frequency    -   RFIC Radio Frequency Integrated Circuit    -   ROM Read Only Memory    -   RRH Remote Radio Head    -   RTT Round Trip Time    -   SMF Session Management Function    -   UDM Unified Data Management    -   UE User Equipment

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein.

What is claimed is:
 1. A system comprising: a radio system comprisingtwo or more Radio Frequency Integrated Circuits, RFICs, wherein eachRFIC comprises: a plurality of antenna elements; Local Oscillator, LO,generation circuitry comprising a frequency divider, the LO generationcircuitry configured to generate a LO signal based on a reference LOsignal from an external LO source; and processing circuitry configuredto, based on the LO signal, upconvert signals to be transmitted via theplurality of antenna elements and/or downconvert signals received viathe plurality of antenna elements; and a processing unit adapted to, fora first RFIC pair comprising two of the two or more RFICs, namely afirst RFIC and a second RFIC: obtain a first near-field powermeasurement for the first RFIC pair via a receive antenna elementcomprised in either the first RFIC or the second RFIC while a testsignal is transmitted via a first transmit antenna element comprised inthe first RFIC and a second transmit antenna element comprised in thesecond RFIC and a phase state of the second RFIC is a first LO phasestate, wherein: the first transmit antenna element is one of theplurality of antenna elements comprised in the first RFIC that isconfigured as a transmit antenna element; the second transmit antennaelement is one of the plurality of antenna elements comprised in thesecond RFIC that is configured as a transmit antenna element; and thereceive antenna element is either: (a) one of the plurality of antennaelements comprised in the first RFIC that is configured as a receiveantenna element or (b) one of the plurality of antenna elementscomprised in the second RFIC that is configured as a receive antennaelement; obtain a second near-field power measurement for the first RFICpair via the receive antenna element while a test signal is transmittedvia the first transmit antenna element and the second transmit antennaelement and the phase state of the second RFIC is a second LO phasestate; determine which of the first LO phase state and the second LOphase state for the second RFIC results in phase alignment between theLO signals for the first RFIC and the second RFIC based on apredetermined relationship between near-field power measurements andphase alignment between the LO signals for the first RFIC and the secondRFIC; and set the phase state of the second RFIC to the determined LOphase state.
 2. The system of claim 1 wherein the second LO phase stateis a state in which a phase of the LO signal for the second RFIC isshifted by 180 degrees relative to the phase of the LO signal for thesecond RFIC when the phase state of the second RFIC is the first LOphase state.
 3. The system of claim 1 wherein the first transmit antennaelement, the second transmit antenna element, and the receive antennaelement are such that a coupling between the first transmit antennaelement and the receive antenna element is symmetrical to a couplingbetween the second transmit antenna element and the receive antennaelement.
 4. The system of claim 1 wherein, for each RFIC of the two ormore RFICs, the plurality of antenna elements comprised in the RFIC aredual-polarized antenna elements, the first antenna element and thesecond transmit antenna elements are configured in a first polarization,and the receive antenna element is configured in a second polarizationwhich is a polarization that is opposite to the first polarization. 5.The system of claim 1 wherein: the predetermined relationship betweenthe near-field power measurements and the phase alignment between the LOsignals for the first RFIC and the second RFIC is that: if the firstnear-field power measurement is greater than the second near-field powermeasurement, then the phases of the LO signals for the first RFIC andthe second RFIC are misaligned when the phase state of the second RFICis the first LO phase state and aligned when the phase state of thesecond RFIC is the second LO phase state; and if the first near-fieldpower measurement is not greater than the second near-field powermeasurement, then the phases of the LO signals for the first RFIC andthe second RFIC are aligned when the phase state of the second RFIC isthe first LO phase state and misaligned when the phase state of thesecond RFIC is the second LO phase state; and the determined LO phasestate for the second RFIC is: the second LO phase state if the firstnear-field power measurement is greater than the second near-field powermeasurement; and the first LO phase state if the first near-field powermeasurement is not greater than the second near-field power measurement.6. The system of claim 1 wherein: the predetermined relationship betweenthe near-field power measurements and the phase alignment between the LOsignals for the first RFIC and the second RFIC is that: if the firstnear-field power measurement is greater than the second near-field powermeasurement, then the phases of the LO signals for the first RFIC andthe second RFIC are aligned when the phase state of the second RFIC isthe first LO phase state and misaligned when the phase state of thesecond RFIC is the second LO phase state; and if the first near-fieldpower measurement is not greater than the second near-field powermeasurement, then the phases of the LO signals for the first RFIC andthe second RFIC are misaligned when the phase state of the second RFICis the first LO phase state and aligned when the phase state of thesecond RFIC is the second LO phase state; and the determined LO phasestate for the second RFIC is: the first LO phase state if the firstnear-field power measurement is greater than the second near-field powermeasurement; and the second LO phase state if the first near-field powermeasurement is not greater than the second near-field power measurement.7. The system of claim 1 wherein the processing unit is further adaptedto, for a second RFIC pair comprising two of the two or more RFICs,namely the first RFIC and a third RFIC: obtain a first near-field powermeasurement for the second RFIC pair via a receive antenna element forthe second RFIC pair that is comprised in either the first RFIC or thethird RFIC while a test signal is transmitted via a first transmitantenna element for the second RFIC pair that is comprised in the firstRFIC and a second transmit antenna element for the second RFIC pair thatis comprised in the third RFIC and a phase state of the third RFIC is afirst LO phase state, wherein: the first transmit antenna element forthe second RFIC pair is one of the plurality of antenna elementscomprised in the first RFIC that is configured as a transmit antennaelement; the second transmit antenna element for the second RFIC pair isone of the plurality of antenna elements comprised in the third RFICthat is configured as a transmit antenna element; and the receiveantenna element for the second RFIC pair is either: (a) one of theplurality of antenna elements comprised in the first RFIC that isconfigured as a receive antenna element or (b) one of the plurality ofantenna elements comprised in the third RFIC that is configured as areceive antenna element; obtain a second near-field power measurementfor the second RFIC pair via the receive antenna element for the secondRFIC pair while a test signal is transmitted via the first transmitantenna element for the second RFIC pair and the second transmit antennaelement for the second RFIC pair and the phase state of the third RFICis a second LO phase state, wherein the second LO phase state is a statein which a phase of the LO signal for the third RFIC is shifted by 180degrees relative to the phase of the LO signal for the third RFIC whenthe phase state of the third RFIC is the first LO phase state; determinewhich of the first LO phase state and the second LO phase state for thethird RFIC results in phase alignment between the LO signals for thefirst RFIC and the third RFIC based on a predetermined relationshipbetween near-field power measurements and phase alignment between the LOsignals for the first RFIC and the third RFIC; and set the phase stateof the third RFIC to the determined LO phase state.
 8. A systemcomprising: a radio system comprising two or more Radio FrequencyIntegrated Circuits, RFICs, wherein each RFIC comprises: a plurality ofantenna elements; Local Oscillator, LO, generation circuitry comprisinga frequency divider, the LO generation circuitry configured to generatea LO signal based on a reference LO signal from an external LO source;and processing circuitry configured to, based on the LO signal,upconvert signals to be transmitted via the plurality of antennaelements and/or downconvert signals received via the plurality ofantenna elements; and a processing unit adapted to, for a first RFICpair comprising two of the two or more RFICs, namely a first RFIC and asecond RFIC: obtain a first near-field power measurement for the firstRFIC pair via a first receive antenna element comprised in the firstRFIC and a second receive antenna element comprised in the second RFICwhile a test signal is transmitted via a transmit antenna elementcomprised in either the first RFIC or the second RFIC and a phase stateof the second RFIC is a first LO phase state, wherein: the first receiveantenna element is one of the plurality of antenna elements comprised inthe first RFIC that is configured as a receive antenna element; thesecond receive antenna element is one of the plurality of antennaelements comprised in the second RFIC that is configured as a receiveantenna element; and the transmit antenna element is either: (a) one ofthe plurality of antenna elements comprised in the first RFIC that isconfigured as a transmit antenna element or (b) one of the plurality ofantenna elements comprised in the second RFIC that is configured as atransmit antenna element; obtain a second near-field power measurementfor the first RFIC pair via the first receive antenna element and thesecond receive antenna element while the test signal is transmitted viathe transmit antenna element and the phase state of the second RFIC is asecond LO phase state; determine which of the first LO phase state andthe second LO phase state for the second RFIC results in phase alignmentbetween the LO signals for the first RFIC and the second RFIC based on apredetermined relationship between near-field power measurements andphase alignment between the LO signals for the first RFIC and the secondRFIC; and set the phase state of the second RFIC to the determined LOphase state.
 9. The system of claim 8 wherein the second LO phase stateis a state in which a phase of the LO signal for the second RFIC isshifted by 180 degrees relative to the phase of the LO signal for thesecond RFIC when the phase state of the second RFIC is the first LOphase state.
 10. The system of claim 8 wherein the first receive antennaelement, the second receive antenna element, and the transmit antennaelement are such that a coupling between the first receive antennaelement and the transmit antenna element is symmetrical to a couplingbetween the second receive antenna element and the transmit antennaelement.
 11. The system of claim 8 wherein, for each RFIC of the two ormore RFICs, the plurality of antenna elements comprised in the RFIC aredual-polarized antenna elements, the first receive antenna element andthe second receive antenna element are configured in a firstpolarization, and the transmit antenna element is configured in a secondpolarization which is a polarization that is opposite to the firstpolarization.
 12. The system of claim 8 wherein: the predeterminedrelationship between near-field power measurements and phase alignmentbetween the LO signals for the first RFIC and the second RFIC is that:if the first near-field power measurement is greater than the secondnear-field power measurement, then the phases of the LO signals for thefirst RFIC and the second RFIC are misaligned when the phase state ofthe second RFIC is the first LO phase state and aligned when the phasestate of the second RFIC is the second LO phase state; and if the firstnear-field power measurement is not greater than the second near-fieldpower measurement, then the phases of the LO signals for the first RFICand the second RFIC are aligned when the phase state of the second RFICis the first LO phase state and misaligned when the phase state of thesecond RFIC is the second LO phase state; and the determined phase statefor the second RFIC is: the second LO phase state if the firstnear-field power measurement is greater than the second near-field powermeasurement; and the first LO phase state if the first near-field powermeasurement is not greater than the second near-field power measurement.13. The system of claim 8 wherein: the predetermined relationshipbetween near-field power measurements and phase alignment between the LOsignals for the first RFIC and the second RFIC is that: if the firstnear-field power measurement is greater than the second near-field powermeasurement, then the phases of the LO signals for the first RFIC andthe second RFIC are aligned when the phase state of the second RFIC isthe first LO phase state and misaligned when the phase state of thesecond RFIC is the second LO phase state; and if the first near-fieldpower measurement is not greater than the second near-field powermeasurement, then the phases of the LO signals for the first RFIC andthe second RFIC are misaligned when the phase state of the second RFICis the first LO phase state and aligned when the phase state of thesecond RFIC is the second LO phase state; and the determined phase statefor the second RFIC is: the first LO phase state if the first near-fieldpower measurement is greater than the second near-field powermeasurement; and the second LO phase state if the first near-field powermeasurement is not greater than the second near-field power measurement.14. The system of claim 8 wherein the processing unit is further adaptedto, for a second RFIC pair comprising two of the two or more RFICs,namely the first RFIC and a third RFIC: obtain a first near-field powermeasurement for the second RFIC pair via a first receive antenna elementfor the second RFIC pair that is comprised in the first RFIC and asecond receive antenna element for the second RFIC pair that iscomprised in the third RFIC while a test signal is transmitted via atransmit antenna element for the second RFIC pair that is comprised ineither the first RFIC or the third RFIC and a phase state of the thirdRFIC is a first LO phase state, wherein: the first receive antennaelement for the second RFIC pair is one of the plurality of antennaelements comprised in the first RFIC that is configured as a receiveantenna element; the second receive antenna element for the second RFICpair is one of the plurality of antenna elements comprised in the thirdRFIC that is configured as a receive antenna element; and the transmitantenna element for the second RFIC pair is either: (a) one of theplurality of antenna elements comprised in the first RFIC that isconfigured as a transmit antenna element or (b) one of the plurality ofantenna elements comprised in the third RFIC that is configured as atransmit antenna element; obtain a second near-field power measurementvia the first receive antenna element for the second RFIC pair and thesecond receive antenna element for the second RFIC pair while a testsignal is transmitted via the transmit antenna element for the secondRFIC pair and the phase state of the third RFIC is a second LO phasestate, wherein the second LO phase state is a state in which a phase ofthe LO signal for the third RFIC is shifted by 180 degrees relative tothe phase of the LO signal for the third RFIC when the phase state ofthe third RFIC is the first LO phase state; determine which of the firstLO phase state and the second LO phase state for the third RFIC resultsin phase alignment between the LO signals for the first RFIC and thethird RFIC based on a predetermined relationship between near-fieldpower measurements and phase alignment between the LO signals for thefirst RFIC and the third RFIC; and set the phase state of the third RFICto the determined LO phase state.
 15. A method for self-testing of asystem comprising a radio system comprising two or more Radio FrequencyIntegrated Circuits, RFICs, each comprising a plurality of antennaelements, Local Oscillator, LO, generation circuitry comprising afrequency divider and being configured to generate a LO signal based ona reference LO signal from an external LO source, and processingcircuitry configured to, based on the LO signal, upconvert signals to betransmitted via the plurality of antenna elements and/or downconvertsignals received via the plurality of antenna elements, wherein themethod comprises, for a first RFIC pair comprising two of the two ormore RFICs, namely a first RFIC and a second RFIC: obtaining a firstnear-field power measurement for the first RFIC pair via a receiveantenna element comprised in either the first RFIC or the second RFICwhile a test signal is transmitted via a first transmit antenna elementcomprised in the first RFIC and a second transmit antenna elementcomprised in the second RFIC and a phase state of the second RFIC is afirst LO phase state, wherein: the first transmit antenna element is oneof the plurality of antenna elements comprised in the first RFIC that isconfigured as a transmit antenna element; the second transmit antennaelement is one of the plurality of antenna elements comprised in thesecond RFIC that is configured as a transmit antenna element; and thereceive antenna element is either: (a) one of the plurality of antennaelements comprised in the first RFIC that is configured as a receiveantenna element or (b) one of the plurality of antenna elementscomprised in the second RFIC that is configured as a receive antennaelement; obtaining a second near-field power measurement for the firstRFIC pair via the receive antenna element while the test signal istransmitted via the first transmit antenna element and the secondtransmit antenna element and the phase state of the second RFIC is asecond LO phase state; determining which of the first LO phase state andthe second LO phase state for the second RFIC results in phase alignmentbetween the LO signals for the first RFIC and the second RFIC based on apredetermined relationship between near-field power measurements andphase alignment between the LO signals for the first RFIC and the secondRFIC; and setting the phase state of the second RFIC to the determinedLO phase state.
 16. The method of claim 15 wherein the second LO phasestate is a state in which a phase of the LO signal for the second RFICis shifted by 180 degrees relative to the phase of the LO signal for thesecond RFIC when the phase state of the second RFIC is the first LOphase state.
 17. The method of claim 15 wherein the first transmitantenna element, the second transmit antenna element, and the receiveantenna element are such that a coupling between the first transmitantenna element and the receive antenna element is symmetrical to acoupling between the second transmit antenna element and the receiveantenna element.
 18. The method of claim 15 wherein, for each RFIC ofthe two or more RFICs, the plurality of antenna elements comprised inthe RFIC are dual-polarized antenna elements, the first transmit antennaelement and the second transmit antenna elements are configured in afirst polarization, and the receive antenna element is configured in asecond polarization which is a polarization that is opposite to thefirst polarization.
 19. The method of claim 15 wherein: thepredetermined relationship between near-field power measurements andphase alignment between the LO signals for the first RFIC and the secondRFIC is that: if the first near-field power measurement is greater thanthe second near-field power measurement, then the phases of the LOsignals for the first RFIC and the second RFIC are misaligned when thephase state of the second RFIC is the first LO phase state and alignedwhen the phase state of the second RFIC is the second LO phase state;and if the first near-field power measurement is not greater than thesecond near-field power measurement, then the phases of the LO signalsfor the first RFIC and the second RFIC are aligned when the phase stateof the second RFIC is the first LO phase state and misaligned when thephase state of the second RFIC is the second LO phase state; anddetermining which of the first LO phase state and the second LO phasestate for the second RFIC results in phase alignment between the LOsignals for the first RFIC and the second RFIC comprises: determiningthat the second LO phase state for the second RFIC results in phasealignment between the LO signals for the first RFIC and the second RFICif the first near-field power measurement is greater than the secondnear-field power measurement; and determining that the first LO phasestate for the second RFIC results in phase alignment between the LOsignals for the first RFIC and the second RFIC if the first near-fieldpower measurement is not greater than the second near-field powermeasurement.
 20. The method of claim 15 wherein: the predeterminedrelationship between near-field power measurements and phase alignmentbetween the LO signals for the first RFIC and the second RFIC is that:if the first near-field power measurement is greater than the secondnear-field power measurement, then the phases of the LO signals for thefirst RFIC and the second RFIC are aligned when the phase state of thesecond RFIC is the first LO phase state and misaligned when the phasestate of the second RFIC is the second LO phase state; and if the firstnear-field power measurement is not greater than the second near-fieldpower measurement, then the phases of the LO signals for the first RFICand the second RFIC are misaligned when the phase state of the secondRFIC is the first LO phase state and aligned when the phase state of thesecond RFIC is the second LO phase state; and determining which of thefirst LO phase state and the second LO phase state for the second RFICresults in phase alignment between the LO signals for the first RFIC andthe second RFIC comprises: determining that the first LO phase state forthe second RFIC results in phase alignment between the LO signals forthe first RFIC and the second RFIC if the first near-field powermeasurement is greater than the second near-field power measurement; anddetermining that the second LO phase state for the second RFIC resultsin phase alignment between the LO signals for the first RFIC and thesecond RFIC if the first near-field power measurement is not greaterthan the second near-field power measurement.